Fiber optic cables are used in a wide variety of applications to carry high data rate communications signals between two (or more) devices. Typically a fiber optic cable will include at least two optical fibers, namely a first optical fiber that carries transmissions from a first device to a second device and a second optical fiber that carries transmissions from the second device to the first device. By providing at least two optical fibers between each pair of devices, duplex communications may be supported without having optical signals travel along the same optical fiber in different directions, which can potentially lead to interference.
Fiber optic “trunk cables” refer to fiber optic cables that are capable of supporting communications between multiple users or devices. Fiber optic trunk cables include at least four optical fibers, and often include a much larger number of optical fibers such as, for example, between twelve and two hundred eighty-eight optical fibers. The optical fibers are typically terminated with connectors such, as for example, multi-fiber push-on (“MPO”) type connectors. The trunk cable may include a transition point where the main cable of the trunk cable is broken out into a plurality of smaller break-out cables that each include a subset of the optical fibers from the main cable. By way of example, a fiber optic trunk cable that has ninety-six optical fibers within the main cable thereof may have eight breakout cables on one or both ends thereof, where each breakout cable includes twelve of the ninety-six optical fibers. An end of each breakout cable may be terminated with a fiber optic connector such as, for example, an MPO connector. The fiber optic connector that terminates each breakout cable may be connected to a mating fiber optic connector of a fiber optic enclosure such as, for example, a fiber optic transceiver, a fiber optic patch panel, a fiber optic shelf enclosure or the like.
FIG. 1 is a perspective view of a conventional fiber optic trunk cable 10. As shown in FIG. 1, the trunk cable 10 includes a main cable 20, a plurality of breakout cables 30-1 through 30-12, a main cable connector 40 and a plurality of breakout cable connectors 50-1 through 50-12. In the depicted embodiment, the main cable 20 includes twenty-four optical fibers, and the main cable connector 40 is a twenty-four optical fiber connector. The main cable 20 includes a breakout section 22 where the main cable 20 splits into the twelve breakout cables 30-1 through 30-12. Each breakout cable 30 includes two optical fibers, and is terminated with a duplex fiber optic connector 50.
In many applications, a fiber optic trunk cable such as trunk cable 10 may be routed into a fiber optic enclosure. Typically the breakout cables 30 are fully received within the fiber optic enclosure, as is a small segment of the main cable 20. Inside the fiber optic enclosure, the connectors 50 on each breakout cables 30 are connected to fiber optic connectors that are within and/or are mounted on the enclosure.
By way of example, as shown in FIG. 2A, a fiber optic shelf unit 100 may be provided that includes a plurality of shelves 110. A fiber optic enclosure 120 may be mounted in each shelf 110 of the shelf unit 100. As shown in FIG. 2B, each fiber optic enclosure 120 may comprise an open box 130 that has a plurality of fiber optic adapters 140 mounted on a front wall 132 thereof, one or more apertures 150 for trunk cables 10 in a back wall 134 thereof, and fiber optic cable routing features 160 within the box 130 that may be used to ensure that the breakout cables 30 are not bent beyond an acceptable bend radius. In such applications, one or more trunk cables 10 may be routed into the interior of the box 130 through the apertures 150 so that the breakout sections 22 of the trunk cables 10 are within the interior of the box 130. Excess length of each breakout cable 30 may be wound around the fiber optic cable routing features 160. The connectors 50 on each breakout cable 30 may be inserted into the rear side of the respective fiber optic adapters 140 that are mounted on the front wall 132. Other fiber optic cables such as fiber optic patch cords (not shown) may then be mounted in the front side of the fiber optic adapters 140 to connect the trunk cable 10 to other fiber optic apparatus (not shown) that the fiber patch cords are connected to. The fiber optic adapters 140 may be any appropriate fiber optic adapters such as, for example, LC adapters, SC adapters, MPO adapters, etc.
Tension may be inadvertently applied to trunk cables such as trunk cable 10 after the trunk cable 10 is installed in a fiber optic enclosure 120. If this occurs, the tension may be transferred to the optical connectors 50. In order reduce or prevent this from occurring, a device known as a trunk cable gland may be mounted in the aperture 150 opening in the back wall 134 of the box 130 to secure the trunk cable 100 to the fiber optic enclosure 120.
FIG. 3 is a perspective view of a conventional trunk cable gland 60. As shown in FIG. 3, the trunk cable gland 60 includes a body 70 that has a cable passage 80 that extends from a first (front) end 72 to a second (back) end 74 of the body 70. The front end 72 of the body 70 has a smaller diameter than a central section 76 of the body 70 and includes a threaded outer surface. A nut 90 is releasably attached to the threaded outer surface.
FIG. 4 is a schematic side view illustrating how the trunk cable gland 60 may be used to support a trunk cable 10 that is fed into a fiber optic enclosure 120. As shown in FIG. 4, an aperture 150 (see FIG. 2) is provided in a sidewall 134 of the fiber optic enclosure 120. The trunk cable gland 60, with the nut 90 thereof removed, is mounted on the main cable 20 of trunk cable 10 so that the main cable goes through the cable passage 80 of the trunk cable gland 60. The breakout cords 30 and an end portion of the main cable 20 of the trunk cable 10 are routed through the aperture 150 in the back wall 134 of the fiber optic enclosure 120, and the front end 72 of the trunk cable gland 60 is also inserted through the aperture 150 in the wall 134. Each breakout cable 30 is threaded through the nut 90 so that the nut 90 may be slid onto the end portion of the main cable 20 until it contacts the front end 72 of the body 70 of trunk cable gland 60. The nut 90 is then threaded onto the front end 72 of the trunk cable gland 60. As the nut 90 is tightened onto the front end 72 of the body 70, the trunk cable gland 60 is pulled forwardly through the aperture 150 until the wall 134 is firmly captured between the nut 90 and the central portion 76 of the body 70, which has a diameter that is larger than the diameter of the aperture 150. In this fashion, the trunk cable gland 60 is securely (and releasably) mounted in the aperture 150 with the trunk cable 10 routed through the trunk cable gland 60 so that the trunk cable gland 60 supports the trunk cable 10 and so that any inadvertent tension or other forces on the trunk cable 10 is not transferred to the optical connectors 50.